I'm going to throw this out here just in case it may be of use to others.
My home has a well, and my issues with rotten egg smell was only with the hot water. When we first moved into the house, there was no rotten egg smell. Now, listen.
I knew the 50 gallon electric water heater was very old and had probably never had the sacrificial anode changed. For those who do not know, the sacrificial anode is a rod of soft metal, often magnesium, or aluminum, or zinc, that corrodes away ever so slowly in an ionic exchange with the water so as not to allow the metal in the steel tank itself to rust away. (Those if you with science degrees may wish to elaborate on this process more thoroughly.) So being pretty handy with plumbing, I got one, and changed it out. In the process, I discovered that the original was completely gone. Disintegrated. Kaput!
Now, here's where it gets interesting. Within 24 hours, we began noticing a rotten egg smell coming from the hot water taps. Somehow, the new anode was causing the smell!
I removed the new rod, and put the cap back in from the old rod. I drained and refilled the tank an within 24 hours, the smell was gone.
I did some research and learned that a by-product of the corrosion of the anode promotes the growth of natural and harmless bacteria in the well water, and a by-product of the bacteria is the sulphur smell. Yuck.
Believe it or not I was able to solve this by installing an electronic anode. It uses just a tiny bit of electricity to protect the steel tank and offers nothing to promote the growth of bacteria.
I've had mine for 7 years now and my old water heater (which the serviceman said was shot and needed to be replaced) is still going strong and soon to be fed with my Rocket Mass Heater/Solar Thermal Water Pre-Heater Hybrid.
This is where I ordered mine from. No regrets whatsoever.
Hope this helps.